psconfig _meta display-set doc missing

[laeti-tia]

It would be good to have a bit of documentation about the psconfig address _meta field display-set that allows for grouping addresses belonging to the same hosts (multiple interfaces).

Usage example:

      "psmp-gn-owd-01.sof.bg.geant.net": {
          "_meta" : {
              "display-name" : "Sofia",
              "display-set" : "sof-bg"
          },
        "host": "Sofia",
        "address": "psmp-gn-owd-01.sof.bg.geant.net",
        "lead-bind-address" : "psmp-gn-bw-01-sof-bg.geant.net",
        "pscheduler-address" : "psmp-gn-bw-01-sof-bg.geant.net",
        "no-agent" : true
      },
  
      "psmp-gn-bw-01-sof-bg.geant.net": {
          "_meta" : {
              "display-name" : "Sofia",
              "display-set" : "sof-bg"
          },
        "host": "Sofia",
        "address": "psmp-gn-bw-01-sof-bg.geant.net",
        "lead-bind-address" : "psmp-gn-bw-01-sof-bg.geant.net",
        "pscheduler-address" : "psmp-gn-bw-01-sof-bg.geant.net",
        "no-agent" : true
      }